Electrical connector



March 15. 1949. E. R. oLsoN 2,464,649

ELECTRICAL CONNECTOR Filed Jan. 12, 1946 l will.' l u Patented Mar. l5,1949 2,464,649 ELECTRICAL CONNECTOR Einar R. Olson, Richmond. Ind.,assignor Belden Manufacturing Company, Chicago, Ill.,

a corporation of Illin ois Application January 12, 1946, Serial No.640,825

3 Claims. 1

The present invention relates to electrical connectors, and particularlyto detachable plug connectors, of the type used for connectingelectrical conductor cords to electrically heated appliances, such astoasters, liat irons, and the like.

Connectors of this general type usually comprise a hollow, elongatedbody of rigid, heat resistant insulating material having two,socket-type con'- tacts supported in side by side relationship withintwo, open ended recesses formed in the connector body. The connectorbody usually comprises two, cooperating half-sections. The individualconductors of the conductor cord with which the connector is used areattached to the socket-type contacts within the insulating body by screwfastenings or other means.

During use o! the conductor cords and connectors of this type, it is avery common practice for the user to eilect the disengagement of theconnector from the appliance with which it is used by jerking or pullingthe conductor cord. This practice is dangerous, especially whenregularly followed, because it almost always results in injury to thecord or to the internal electrical connections and sometimes even to theuser. However, the appliance is frequently hot, and it is diiiicult toconvince users not to jerk or pull the cord. As a result, it has beenfound highly desirable to provide connectors of this style with a strainrelief means which shall be effective to transmit tensional stressesapplied to the cord directly to the connector body, thereby relievingthe electrical connections from strain.

Various arrangements are in use and others have been proposed, but noneis completely satisiactory. The principal object of the invention,therefore, is to provide an improved strain relief, for use inconjunction with connectors of the class described, which shall be moreeliicient and more reliable in operation than the previously knowndevices, and which, at the same time, shall be simpler and easier toassemble and install in the connectors with which it is used. The meanswhereby this object is attained, and other objects and advantages of theinvention, will be made more apparent in the accompanying drawings andthe following description of one illustrative embodiment of theinvention.

in the drawings,

Fig. 1 is a plan view showing the strain relief of the invention asinstalled in a connector of the class described. One of the halfsections of the connector body has been cut away to better illustratethe features of the device;

Fig. 2 is a sectional view on the general line 2-2 of Fig. 1;

Figs. 3, 4, and 5 are fragmentary views illustrating three successivesteps in preparing the ends 'of a conductor cord for use with the strainrelief of the present invention; and

Fig. 6 is a perspective view showing the next succeeding step in themanufacture of the strain relief of the invention.

The body 9 of the connector illustrated in the drawings comprises two,generally rectangularly shaped, cooperating, half sections II o! a heatresisting insulating material, which are adapted to be securely heldtogether in face to face relation, when the connector is assembled, by apair of screw fastenings I3, or equivalent means. The opposed faces ofthe two cooperating half sections I I are hollowed out so as to dene inthe assembled connector two; generally parallel, elongated.. recesses I5for receiving two, socket-type, spring contacts I1, which are adapted tocooperate with contact pins or the like, forming a part of the appliancewith which the connector is used. The

contacts I1 are of conventional type, and the recesses I5 are so formedthat the contacts I1 are securely held against any substantiallylongitudinal movement relative to the plug body when the connector isassembled. The recesses I5 are, ofcourse, open at the outer end to admitthe cooperating contact pins or the like.

The conductor cord I9 used in conjunction with the connector illustratedin the drawings is of the usual duplex or two conductor type, and isprovided with a braided or rubber Jacketed outer covering. Each of theconductors making up the conductor cord I9 includes a metallic cable 2lwhich is surrounded by a suitable insulating sleeve 23, which isdesirably of asbestos or of some other heat-resisting insulatingmaterial. The conductor cord I9 is admitted to the interior of theconnector body 9 through a generally cylindrical,

` cord receiving passageway 25 which extends thereinto. The inner end ofthe cord receiving passage- Way 25 connects with the two, parallel,contact receiving recesses I5 through branch passageways 2l, whichextend substantially at right angles to the cord receiving passagewaysI5 and the central axis of the connector body 9.

To minimize bending and kinking of the connector cord adjacent theconnector body 9, the connector desirably includes an axially flexibleprotector spring 29, the lower coils 3l of which are of increaseddiameter and are adapted to engage an annular recess 33 formed as anenlargement of the cord receiving passageway 25,'so as to mechanicallyconnect the spring 29 to the connector body 9. A ferrule 35 may beprovided at the outer end of the protector spring for engaging the cord.

In the embodying of the strain relief of the invention into a connectorof this type, the braided covering is ilrst removed from the con' ductorcord I9, so as to expose the two insulated conductors constituting suchcord, for a distance about equal to the length of the body'portion 9 ofthe connector, see Fig, 3. The braid end is then wrapped with thread orthe like, as illustrated at 31, to prevent unravelling, and theinsulating covering 23 on the two cord conductors is also wrapped tostiffen the insulation and to prevent it from becoming displaced, asillustrated in Fig. 4. A length of the conductor cables suitable forengagement with the connector contacts I1 is bared following the braidremoval operation, arid preferably preceding the wrapping operation.

Following the wrapping operation, which brings the prepared cordstructure into the condition illustrated in Fig. 4, a flat, elongatedstripor bar 39, of rectangular cross section and made of relativelystrong and rigid insulating material, such as a hard fiber or a moldedresin product, is placed between the two wrapped ends of the insulatedconductors making up the conductor cord, and those ends are wound aroundthis strip in opposite directions, as indicated by the dotted arrows inFig. 5, to produce the structure illustrated in Fig. 6. The insulatingstrip 39 should have a length which is substantially greater than thecord receiving opening 25, and it should have a thickness which is suchthat the ends of the insulated conductors which are wound around thestrip 39, and the strip itself, will be tightly compressed when the twohalf sections Il of the connector body are assembled. For the usual typestructure wherein the branch passageways 21 have a thickness about twicethe diameter of the individual insulated cord conductors, this meansthat the strip 39 should have a thickness which is about equal to thediameter of the insulated cord conductors. The strip or bar 39, aspreviously stated, should be of relatively fiat construction, anddesirably should have a width which is at least about one and a halftimes its thickness.

During final assembly of the strain relief means, care should beexercised to make sure that the fiat sides of the bar 39 will extendsubstantially parallel to the engaging faces of the cooperating halfsections ll of the connector body. The socket-type contacts l1 may beattached to the cord conductors either before or after the strain reliefbar 39 has been put into place.

When the connector has been completely assembled, the various componentparts thereof will be in the position shown in Figs. 1 and 2. Anytensional strain applied to the cord I9 will be transmitted to the body9 of the connector through the strain relief bar 39 and the conductorwrapping applied to that bar. Stressing and possible injury to theelectrical connections within the connector is thereby avoided. Becausethe two ends of the cord conductors which engage the strain relief bar39 are wrapped around that bar in opposite directions, any tendency ofthe bar 39 to rotate substantially when stress is applied to theconductor cord is obviated by the oppositely disposed forces set up. Theshape of the bar, which produces sharp corners which bite into the cordconductors, and particularly its greater width than thickness, isimportant in obtaining the objects of the invention.

The strain relief construction of the invention, while very simple indesign, inexpensive to manufacture, and easy to assemble, has provenhighly efficient. Further, in contrast with many of the known strainresisting arrangements, the construction of the invention does not loseits strain resisting ability after the connector wherein it has beeninstalled has been in use for some time. The oppositely acting forcesproduced during the strain resisting operation make the effectiveness ofthe device independent of the strength of the cord insulation or of anysupplementary wrapping, or other means, as is the case in some of theprior art structures, and thus provide a, strain relief which isoperable and effective so long as the cord conductors themselves areintact. The features of the invention. which are believed to be new, areexpressly set forth in the appended claims. y

I claim the following as my invention:

1,'In an electrical connector of the class vdescribed, a pair of fiat,cooperating, half sections of insulating material assemblage in face toface contact to provide a connector body, said half sections beingprovided with opposed recesses which provide, when said half sectionsare assembled, a pair of spaced-apart contact receiving recesses, acentrally disposed, conductor cord receiving passageway, andtransversely extending, branch passageways which connect said contactreceiving recesses and said cord receiving passageway, contact membersoccupying saidcontact receiving recesses, a conductor cord, having apair of insulated conductors connected respectively to said contact'members occupying said cord receiving passageway, and an elongated,strain relief bar, which is generally rectangular in cross section andwhich has a width which is substantially greater than its thicknessextending across said cord receiving passageway and into each of saidtransversely extending branch passageways, sai-d bar being disposedfiatwise relative to the plane of the engaging faces of the halfsectlonsof said connector body, a portion of one of the insulatedconductors comprising said conductor cord also Yoccupying each of saidbranch passageways, the conductor portions occupying said branchpassageways being wrapped around said strain relief bar in oppositedirections, and the relative proportions of said branch passageways,said bar, and said conductors being such that said conductors and saidstrain relief bar are tightly compressed and held in position by theco-operating half sections of the connector body when said connector isassembled,

2. In an electrical connector of the class described, a pair of nat,cooperating, half sections of insulating material assemblable .in faceto face contact to provide a connector body, said half sections beingprovided with opposed recesses which provide, when said half sectionsare assembled, a pair of spaced-apart, contact receiving recesses, acentrally disposed, conductor cord receiving passageway, andtransversely extending, branch passageways which connect said contactreceiving recesses and said cord receiving passageway, contact membersoccupying said con.- t-act receiving recesses, a conductor cord, havinga pair of insulated conductors connected respectively to said contactmembers, occupying said cord receiving passageway, and an elongated,strain relief bar of insulating material which extends across said cordreceiving passageway and into each of said branch passageways, saidstrain relief bar being rectangular in cross section, with sharpcorners, having a. width which is at least about one and one-half Vtimesits thickness, and being disposed iiatwise relative to the plane of theengaging faces of the half sections of said connector body, the endportion of each one of the insulated conductors comprising saidconductor cord Ialso occupying-one of said branch passageways, said endportions being wrapped around said strain relief bar in oppositedirections, and the relative proportions of said branch passageways,said bar and said insulated conductors being such that said end portionsand said strain relief bar are tightly engaged by the cooperating halfsections of the connector body when said connector is assembled.

3. In an electrical connector of .the class described, a pair yof at,(so-operating, half sections of insulating material -assemblable in faceIto face contact to provide a connector body, said half sections beingprovided with opposed recesses which provide, when said half sectionsare assembled, a pair of spaced-apart contact receiving recesses, acentrally disposed, conductor cord receiving passageway, and atransversely extending passageway which connects said contact receivingrecesses and said cord receiving passageway, contact members occupyingsaid contact receiving recesses, a conductor cord having a pair ofinsulated conductors, each of which is connected to one of said contactmembers, said conductors occupying said cord receiving passageway, andan elongated, strain relief bar which is generally rectangular incross-section and which has sharp edges extending across said cordreceiv- REFERENCES CITED The following references are of record in thefile of this patent:

UNITED STATES PATENTS Number Name Date 2,178,621 Andre Nov. '7, 1939FOREIGN PATENTS Number Country Date 633,042 France 1927 169,973 France s1934

